Some 75% of off-trade outlets visited for test purchases of alcohol by the company’s mystery shoppers asked for official ID.
This compared with a success rate of 70% for the whole of 2009.
Supermarkets scored 78% in the first half of this year, against 71% in 2009, while convenience stores scored 75% for January-June 2010, versus 72% in 2009.
The demise of First Quench meant only 62 store visits were made to specialist off-licences in the first six months of 2010, against more than 1,500 in 2009. The success rate was up to 74% from 65%.
Scotland had the best overall pass rate with 82%, followed by London on 80%.
The Midlands won the must-try-harder prize with 70%.
Serve Legal uses young mystery shoppers of legal drinking age to check that age verification policies are being enforced, on behalf of clients including several major high street chains.
Director Charlie Mowat said: “Performance improves due to awareness among staff that they are being randomly tested, increased focus from management on under-age legislation, and specific actions suggested.”